Lead-free piezo printhead using thinned bulk material

ABSTRACT

An apparatus for a lead-free piezoelectric ink-jet printhead is disclosed. Piezoelectric printheads, while more expensive are favored because they use a wider variety of inks. The piezoelectric printhead includes a diaphragm, a plurality of piezoelectric actuators comprising a lead-free piezoelectric material, at least one nozzle, at least one ink chamber, a top electrode, and a drive circuit. The deflection of the diaphragm on the body chamber contributes to a pressure pulse that is used to eject a drop of liquid from the nozzle. According to an exemplary embodiment, a lead-free piezoelectric printhead operated at smaller thicknesses and significantly higher electric fields is disclosed, along with methods of making such printheads.

This application is a Division of U.S. patent application Ser. No.15/611,179, filed Jun. 1, 2017, by Peter J. Nystrom et al., and isincorporated herein by reference in its entirety.

TECHNICAL FIELD

The present application is related to the field of ink-jet printingdevices and more particularly to methods and structures for a lead-freepiezoelectric ink-jet printhead.

BACKGROUND

Drop on demand ink-jet technology is widely used in the printingindustry. Printers using drop on demand ink-jet technology may use aplurality (i.e. an array) of electrostatic actuators, piezoelectricactuators, or thermal actuators to eject ink from a plurality of nozzlesin an aperture plate (nozzle plate). Even though they are more expensiveto manufacture than thermal ink jets, piezoelectric ink jets aregenerally favored, for example, because they can use a wider variety ofinks.

Piezoelectric ink-jet printheads include an array of actuators (i.e.piezoelectric elements or transducers), which are selectively operatedto eject ink onto a print medium to form a printed image. Piezoelectricink-jet printheads generally also include a flexible diaphragm to whichthe array of piezoelectric elements is bonded, and an adjacent bodychamber or ink chamber. The diaphragm may be a metal layer thatfunctions as a lower electrode that is common to a plurality ofactuators, or a non-metal layer coated with a metal layer that providesan individual, electrically conductive lower electrode for eachactuator. When a voltage is applied across one of the actuators, theactuator bends or deflects, causing the diaphragm to flex, which mayeither fill the body chamber with ink or eject a quantity of ink fromthe chamber through a nozzle, depending on the polarity of theelectrical signal.

Generally, each actuator is aligned with each body chamber and nozzle.Thus, one method of improving the printing resolution of an ink-jetprinter employing piezoelectric ink-jet technology is by increasing thedensity of the actuators and their corresponding nozzles.

However, forming ink-jet printheads becomes increasingly more difficultwith decreasing actuator sizes and thicknesses. While microelectronicfabrication of printhead structures would provide precise control of theresulting structures, such methods are volume sensitive and capitalintensive, which may preclude their use for low volume or customproducts.

Alternatively, current piezoelectric ink jet printheads may use a bulkpiezo transducer material, such as lead zirconate titanate (PZT) systemthat is between 50 μm and 100 μm thick, bonded to stainless steeldiaphragms that are between 20 μm and 40 μm thick and square orparallelogram body chambers with dimensions on the order of 400 to 800μm per side. Such bulk piezo material is typically pre-cut and thenbonded to the diaphragm using an epoxy process. Many current printheadsuse the lead-containing PZT material, which is non-green but iscurrently permitted by the Restriction of Hazardous Substances Directiveunder exemptions that will eventually expire. Thus, lead-free piezomaterials for printhead applications are desirable.

One lead-free bulk actuator material alternative to PZT is a bismuthsodium potassium titanate (BNKT) based material system. When operated athigh electric fields, a BNKT-based lead-free piezo material can givegood actuator performance.

However, in order to produce such high electric fields using reasonablevoltage levels (less than 100 to 120 volts peak-to-peak), the materialmust be significantly thinner than is currently used. Moreover, theBNKT-based lead-free actuator materials that are thin enough to be usedin printheads are also too thin and fragile to be manufactured andhandled in a free-standing state, then diced and bonded using existingmethods.

Thus, new lead-free piezoelectric printheads and methods for making suchprintheads are desirable.

INCORPORATION BY REFERENCE

The following references, the disclosures of which are incorporatedherein by reference in their entireties, are mentioned:

U.S. Pat. No. 6,955,419, issued Oct. 18, 2005, by Andrews et al.,entitled “INK JET APPARATUS”;

U.S. Pat. No. 6,987,348, issued Jan. 17, 2006, by Buhler et al.,entitled “PIEZOELECTRIC TRANSDUCERS”;

U.S. Pat. No. 7,048,361, issued May 23, 2006, by Schmachtenberg, III etal., entitled “INK JET APPARATUS”; and

U.S. patent application Ser. No. 14/851,422 filed Sep. 11, 2015 entitled“INTEGRATED THIN FILM PIEZOELECTRIC PRINTHEAD”; and

U.S. patent application Ser. No. 15/141,229, filed Apr. 28, 2016,entitled “INTEGRATED PIEZO PRINTHEAD”, incorporated herein by referencein their entirety.

BRIEF DESCRIPTION

In one embodiment of this disclosure, described is a piezoelectricink-jet printhead comprising: a diaphragm; a plurality of piezoelectricactuators wherein each actuator comprises a lead-free piezoelectricmaterial, a first electrode adjacent to a first side of thepiezoelectric material, and a second electrode adjacent to a second sideof the piezoelectric material; at least one nozzle; at least one bodychamber; and a drive circuit that generates an electrical signal acrossone or more of the plurality of piezoelectric actuators.

In another embodiment of this disclosure, described is a method forfabricating a piezoelectric ink-jet printhead comprising a lead-freepiezoelectric material, the method comprising: bonding a piezoelectricmaterial to a diaphragm-plus-body assembly, wherein the piezoelectricmaterial is plated with a first electrode material on a first side priorto bonding; thinning the piezoelectric material to a first thickness;plating the piezoelectric material on a second side with a secondelectrode material; and dicing the piezoelectric material into printheadsized pieces. In particular embodiments, the method further comprisesplating the piezoelectric material on a first side with a firstelectrode material prior to bonding the piezoelectric material to adiaphragm-plus-body assembly.

In still another embodiment of this disclosure, described is a methodfor fabricating a piezoelectric ink-jet printhead comprising a lead-freepiezoelectric material, the method comprising: mounting a piezoelectricmaterial onto a first intermediate substrate, wherein the piezoelectricmaterial is plated on a first side with a first electrode material priorto mounting; thinning the piezoelectric material to a first thickness;plating the piezoelectric material on a second side with a secondelectrode material; dicing the plated piezoelectric material intoindividual actuators; and bonding the diced piezoelectric actuators to adiaphragm-plus-body assembly.

In particular embodiments, the method further comprises plating a firstside of the piezoelectric material with a first electrode material priorto mounting the piezoelectric material onto the first intermediatesubstrate.

In further embodiments, the method also comprises: mounting the platedpiezoelectric material onto a second intermediate substrate afterplating the piezoelectric material on a second side with a secondelectrode material; and unmounting the plating piezoelectric materialfrom the first intermediate substrate.

BRIEF DESCRIPTION OF THE DRAWINGS

The exemplary embodiments may take form in various components andarrangements of components, and in various steps and arrangements ofsteps. The drawings are only for purposes of illustrating the preferredembodiments and are not to be construed as limiting the presentexemplary embodiment.

FIG. 1 depicts an exemplary embodiment of a piezoelectric printhead;

FIG. 2 depicts an exemplary embodiment of a piezoelectric printhead withan attached drive circuit;

FIG. 3 depicts an exemplary embodiment of a piezoelectric printhead froma different perspective;

FIG. 4 is a phase diagram for the typical BNKT morphotropic system,specifically for the (Bi_(1/2)Na_(1/2))TiO₃—(Bi_(1/2)K_(1/2))TiO₃ solidsolution.

FIGS. 5A-5C illustrate potential electrical signals or bias waveformsthat may be applied by the drive circuit according to an embodiment ofthe present teachings;

FIG. 6 is a perspective depiction of a printer including a printheadaccording to an embodiment of the present teachings;

FIG. 7 is a flow chart illustrating an exemplary method of fabricating alead-free piezoelectric printhead; and

FIGS. 8A-8E illustrate a series of steps used to fabricate apiezoelectric printhead according to an exemplary embodiment of thisdisclosure.

FIG. 9 is a flow chart illustrating a second exemplary method offabricating a lead-free piezoelectric printhead;

FIGS. 10A-10F illustrate a series of steps used to fabricate apiezoelectric printhead according to the method shown in FIG. 9;

FIG. 11 is a flow chart illustrating a third exemplary method offabricating a lead-free piezoelectric printhead; and

FIGS. 12A-12H illustrate a series of steps used to fabricate apiezoelectric printhead according to the method shown in FIG. 11.

It should be noted that some details of the figures have been simplifiedand are drawn to facilitate understanding of the present teachingsrather than to maintain strict structural accuracy, detail, and scale.

DETAILED DESCRIPTION

Reference will now be made in detail to exemplary embodiments of thepresent teachings, examples of which are illustrated in the accompanyingdrawings. Wherever possible, the same reference numbers will be usedthroughout the drawings to refer to the same or like parts.

As used herein, unless otherwise specified, the word “printer”encompasses any apparatus that performs a print outputting function forany purpose, such as a digital copier, bookmaking machine, facsimilemachine, a multi-function machine, electrostatographic device, etc.

According to an exemplary embodiment described herein, provided is alead-free piezoelectric printhead system that retains the use ofexisting low-cost adhesive-based jet stack fabrication processes withpolymers and metal layers. A jet stack generally comprises a pluralityof plates or membranes that form channels through which ink flows intoan ink or body chamber and out through a nozzle. The approach describedherein avoids the cost and complexity of a MEMS-based fabricationprocess, and provides a lead-free alternative to current lead-containingprinthead technologies. Here, relatively thick bulk lead-freepiezoelectric material is bonded to a diaphragm or a diaphragm-plus-bodyassembly, then thinned to the desirable thickness range in accordancewith the present teachings.

As shown in FIG. 1, provided is a piezoelectric printhead arraystructure 10, the structure including an array of individual actuators26 bonded to a diaphragm-plus-body assembly 30. The assembly 30 includesa diaphragm 32, a plurality of body or ink chambers 34 enclosed by walls36, an aperture plate 40, and a plurality of nozzles 38. Walls 36 may bean external wall 36A with at least one side not facing or in contactwith interior of the ink chambers 34, or may be an internal wall 36B,with at least two sides forming the sides of the ink chamber 34. Eachindividual actuator 26 is bonded to the diaphragm 32, and comprises atop electrode 22, a bottom electrode 24, and a piezoelectric material20. Generally, each actuator 26 is aligned with a single ink chamber 34and nozzle 38 as shown. In particular embodiments, the bottom electrode24 can be common to a plurality of individual actuators 26, as shown inFIG. 1.

According to an exemplary embodiment, the piezoelectric material 20 is alead-free formulation comprising bismuth sodium potassium titanate(BNKT). In particular embodiments, the BNKT is an oxide (Bi—Na—K—Ti—O),i.e. an oxide that may be of the compositionBi_(v)Na_(w)K_(x)Ti_(y)O_(z), where “v” ranges from 0 to 0.5 (i.e.,0˜0.5, where the range of the Bi component is from 0 to 0.5 mol), “w” isin the range of about 0.5˜1, “x” is in the range of about 0˜0.5, “y” isin the range of about 0.5˜1, and “z” is in the range of about 1.5˜3.5.

In various embodiments, the piezoelectric material 20 may furthercomprise one or more additional compounds, such as bismuth magnesiumtitanate (BMT) and niobium potassium sodium (KNN). BMT and KNN may beoxides (i.e. have the formulation Bi—Mg—Ti—O and K—Na—Nb—Orespectively). In particular embodiments, BMT may be in the formBi_(a)Mg_(b)Ti_(c)O_(d), where “a” is in the range of from about 0.5˜1,“b” is in the range of from about 0˜0.5, “c” is in the range of fromabout 0˜0.5, and “d” is in the range of from about 1.5˜3.5. In furtherembodiments, KNN may be in the form of K_(e)Na_(f)Nb_(g)O_(h). where “e”is in the range of from about 0˜0.6, “f” is in the range of from about0˜0.6, “g” is in the range of from about 0.5˜1.5, and “h” is in therange of from about 1.5˜3.5.

In various embodiments, the lead-free piezoelectric material 20comprises between 90 and 100 mol % of BNKT, or between 95 and 100 mol %BNKT, or between 90 and 99.9 mol % BNKT, or between 95 and 99.9 mol %BNKT.

In various embodiments, the lead-free piezoelectric material 20comprises between 90 and 100 mol % of KNN, or between 95 and 100 mol %KNN, or between 90 and 99.9 mol % KNN, or between 95 and 99.9 mol % KNN.

In further embodiments, the lead-free piezoelectric material 20comprises between 0 and 10 mol % of an additive, such as BMT or KNN, orbetween 0 and 5 mol % of an additive, or between 5 and 10 mol % of anadditive.

According to an exemplary embodiment, the piezoelectric material 20 in acompleted ink-jet printhead 10 may have a thickness of from about 2 μmto about 50 μm, or from about 4 μm to about 45 μm, or from 8 μm to about40 μm, or preferably from about 10 μm to about 20 μm.

In various embodiments, the diaphragm 32 may be composed of a metal, apolymer, a ceramic, glass, or silicon. In particular embodiments, thediaphragm is composed of steel.

According to an exemplary embodiment, the diaphragm 32 in a completedink-jet printhead 10 may have a thickness of from about 2 μm to about 30μm, or from about 4 μm to about 28 μm, or from about 10 μm to about 25μm. In particular embodiments, the thickness of the diaphragm 32 is fromabout 10 μm to about 25 μm.

In particular embodiments, the piezoelectric material may be plated onone or more sides with one or more electrode material compositions. Forexample, the piezoelectric material may be plated on a first side with afirst electrode material, and plated on a second side with a secondelectrode material. In particular embodiments, the one or more electrodematerials may be identical. In other embodiments, the one or moreelectrode materials may be different. In some embodiments, theelectrodes 22, 24 may comprise a metal, such as copper, gold, titanium,nickel, platinum, chromium, aluminum, or a metal alloy such as Pt—Pd orAg—Pd, or an electrically conductive non-metal. The electrodes 22, 24may have a thickness of from about 100 nm (0.1 μm) to about 1100 nm (1.1μm). The electrode layers 22, 24 may be formed using sputtering,chemical vapor deposition, electroplating, or another suitable process.

The remainder of the diaphragm-plus-body assembly or jet stack 30,including the aperture plate 40, walls 36, nozzles 38, ink inlet 50(FIG. 3), and body chambers 34 may be made in accordance with commonpractices known in the art. The completed printhead may include otherink chambers, ink paths, ink reservoirs, electrical structures thatserve as drive electronics, or other electrical or mechanical structuresrelated to the functionality, appearance, or attachment of theprinthead.

As shown in FIG. 2, a drive circuit 42 applies electrical signal viaconnections 44 between the top plate (or top electrode) 22 and thebottom electrode 24. Additionally, when the actuators are bonded to thediaphragm 32, the diaphragm 32 also acts as a common plane for aplurality of the printhead actuators 26. In particular embodiments, thedrive circuit 42 may comprise an application-specific integrated circuit(ASIC) that provides control functions over groups of actuators, as wellas specific circuitry to drive the response of the piezoelectric system.The electrical signal energizes the lead-free piezoelectric material 20,which causes the piezoelectric material 20 and diaphragm 32 to deflect,or bend, over the associated ink chamber 34 creating a pressure pulsewithin the chamber 34. Depending on the electrical signal generated bythe drive circuit 42, the actuators 26 deflect in one direction to drawink into the body chamber 34, or deflect in another direction to ejectink in the body chamber 34 out through the nozzle 38.

According to an exemplary embodiment, each actuator 26 may beindividually addressed by one or more drive circuits 42 via connections44, allowing each actuator 26 to be operated independently. Addressingindividual actuators 26 may be accomplished by a number of means,including blanket metal scribing, etching individual actuators 26,chemical etching, or patterning to form electrodes directly. Inparticular, the patterning can include mechanical sawing (i.e. dicing),scribing and then breaking, laser cutting, waterjet cutting, and othermechanical singulation of the individual actuators 26.

With reference to FIG. 3, a side-view cross-section of an ink-jetprinthead showing an individual actuator 26 and diaphragm-plus-bodyassembly 30 is illustrated. As shown, the diaphragm-plus-body assemblymay further include an ink inlet 50, which allows ink to move from anink source (not shown) through the inlet 50 and into the body chamber34. As discussed above, the drive circuit 42 (FIG. 2) generates anelectrical signal or voltage across the piezoelectric material 20,causing the diaphragm 32 to deflect in a particular direction. Dependingon the electrical signal applied, the diaphragm may deflect and causeink from an ink source (not shown) to be drawn through an ink inlet 50into the body chamber 34 associated with that actuator 26.Alternatively, the electrical signal generated may cause the diaphragm32 to deflect and cause ink in the body chamber 34 associated with thatactuator 26 to be ejected out of the nozzle 38.

With reference to FIG. 4, a phase diagram for the typical BNKTmorphotropic system, specifically for the(Bi_(1/2)Na_(1/2))TiO₃—(Bi_(1/2)K_(1/2))TiO₃ solid solution, is shown.Piezoelectric compositions, such as PZT and the lead-free systemsdiscussed herein, are typically chosen to be close to a morphotropicboundary (MPB) in order to improve poling and net piezoelectricdisplacement. During normal operation of a piezoelectric printhead, thepiezoelectric material would be poled, and the actuator would beoperated with positive and negative pulses to control both the reservoir(i.e. body chamber 34) levels and ejection. Piezoelectric materialscontain Weiss domains (regions of locally aligned dipoles) that mayrandomly oriented (and therefore exhibit no net piezoelectric effect ordisplacement), but become aligned by poling the material. During poling,a very strong electric field is applied across the material, whichorients all the dipoles in the direction of the field. After theelectric field is removed, the dipoles of the material generally remainroughly oriented with the electric field that was applied, but maybecome de-poled if it is subjected to another high electric field (i.e.an electric field above the coercive field level) in a differentdirection, or if the material is exposed to a temperature above theCurie temperature (i.e. de-poling temperature).

However, as compared to PZT, the traditional ink-jet printheadpiezoelectric material, the lead-free BNKT system including BNKT-BMT andBNKT-KNN systems have high electric field responses with significantlydifferent electromechanical behavior. The disclosed systems requirehigher electric fields and operation close to or above the coercivefields of traditional materials. In the currently described systems, notraditional poling is required, and the issues of de-poling andproximity of the de-poling temperature are not a concern. However, inany piezoelectric printhead system, the electromechanical behavior isimportant because the pressure pulse created by the deflection of thepiezoelectric material and the diaphragm must be sufficient to achieve areasonable ink ejection power and drop speed. In other words, theelectrical signal generated across the piezoelectric material must besufficient to generate a pressure pulse that both quickly draws ink intothe ink chamber and quickly ejects ink in the ink chamber out throughthe nozzle.

According to an exemplary embodiment, the higher operating fields caninduce larger displacements. However, as these operating fields may beabove the coercive fields for the lead-free composition, the lead-freepiezoelectric composition may be altered with an additive. In particularembodiments, a lead-free piezoelectric material comprising BNKT may bemodified with BMT or KNN, which provides flexibility in the operation ofthe actuator and optimizes the actuators in conjunction with theelectrical drive circuit and drive conditions. Specifically, theaddition of an additional compound, such as BMT, can lower thetransition temperature to the pseudo-cubic (or relaxor) phase seen inFIG. 4. This phase is not piezoelectric under ambient conditions, but afield-induced transition to a piezoelectric phase can occur upon theapplication of an electric field. This allows for a greater net changein polarization and displacement (i.e. deflection) as compared to theunmodified BNKT. When the electric field is removed, the polarizationand displacement then go back to zero.

However, while BNKT-BMT piezoelectric composition gives the advantage oflarger net displacements, which is important for fluid ejection, thedisplacement is always in the same direction (as in an electrostrictivematerial). In order for the drive circuit to deflect the membrane (i.e.diaphragm) in the opposite direction, one of two strategies can beemployed: (1) a DC bias mode; (2) a mixed-mode.

In the DC bias mode, the piezoelectric material may be operated under aDC bias, as illustrated in FIGS. 5A-5C. With reference to FIGS. 5A, 5B,and 5C, a traditional bi-directional waveform, a waveform with partialbias, and a waveform with full bias are shown respectively. As shown inFIG. 5A, the electrical signal is a traditional bi-directional waveform,with a starting value 62A of zero volts (i.e. zero bias), a positivepeak 60A and a negative peak 64A. Similarly, FIGS. 5B and 5C havepositive peaks 60B and 60C, and negative peaks 64B and 64C,respectively. However, unlike FIG. 5A, FIGS. 5B and 5C have a biasvoltages 62B and 62C, respectively. In particular embodiments, theelectrical signal generated across the one or more of the plurality ofpiezoelectric actuators 26 has a bias such that the voltage level in onedirection is at least 1.5 times the absolute value of the voltageapplied in the opposite direction (i.e. peak 60B, 60C is at least 1.5times the absolute value of peak 64B, 64C). In other embodiments, theelectrical signal has a bias such that the voltage level applies in onedirection is at least 2 times the absolute value of the voltage appliedin the opposite direction. In still further embodiments, the electricalsignal generated across the piezoelectric actuators 26 may have a biassuch that the voltage applied is completely in one direction. As usedherein, the term “direction” refers to the polarity of the appliedvoltage. Thus, “one direction” may be a positive voltage, and another“direction negative, and vice versa.

In an exemplary embodiment, the electrical field or signal generatedacross the one or more of the plurality of the piezoelectric actuators26 is from about 3 volts to about 10 volts per μm of the piezoelectricalmaterial thickness. For example, in a printhead 10 comprising aplurality of piezoelectric actuators 26 with a lead-free piezoelectricmaterial having a thickness of approximately 20 μm, the electricalsignal generated across the actuators 26 by the drive circuit 42 may befrom about 60 volts to about 200 volts, in either a positive or negativedirection (i.e. ±200 volts). Additionally, if the drive circuit has abias voltage of, for example, +25 volts, then the drive circuit 42 mayapply an electrical signal that ranges from about +225 volts to about−175 volts.

The waveforms shown in FIGS. 5A-5C represent the general types ofelectrical signals generated by the drive circuit, which can energizethe piezoelectric material causing it to deflect in a particulardirection. However, other waveforms of various peaks, biases, ranges,durations, and frequencies are also contemplated.

During the DC bias mode of operation, the phase transition of themodified lead-free composition can be used to drive the liquid ejectionsfrom the ink chamber, and the fluid levels in the chamber can becontrolled by dropping the bias to zero (i.e. negative relative to thebias), which results in displacement in the opposite direction. In otherwords, the phase transition at or above the bias voltage is used toeject ink from the ink chamber, while dropping the voltage below thebias voltage is used to draw ink from an ink source into the ink chamberthrough an inlet. In particular embodiments, this mode of operation isused with lead-free compositions, such as BNKT, that have relativelyhigher levels of additives, such as BMT. For example, in someembodiments, this mode of operation is appropriate for a BNKT-BMTpiezoelectric composition containing at least 3 mol % of BMT, or between3 mol % and 5 mol % of BMT.

In the mixed-mode of operation, the piezoelectric material may be haveboth piezoelectric and field-induced electromechanical behavior. Atlower levels of additives (such as BMT or KNN), the electromechanicalbehavior of the lead-free composition is mixed. More specifically, thevarious compositions of BNKT with either BMT or KNN are a mix ofpiezoelectric and relaxor phases, and thus some pure piezoelectriccharacter is maintained. Therefore, small negative biases, below thepiezoelectric coercive field or the field-induced phase transitionlevel, could be used for the negative displacement to set the liquidlevels within the ink chamber, while large positive fields that yieldthe large displacements associated with the field induced phasetransition can be used to drive the liquid ejection.

With reference to FIG. 6, a printer 70 is depicted including a printerhousing 72 into which at least one printhead 74 embodying the presentteachings has been installed. The housing 72 may encase the printhead74. During operation, ink 76 is ejected from one or more printheads 74.The printhead 74 is operated in accordance with digital instructions tocreate a desired image on a print medium 78 such as a paper sheet,plastic, etc. In other words, based on the digital instructions, thedrive circuits 42 eject ink from the ink chambers 34 onto the printmedium 78. The printhead 74 may move back and forth relative to theprint medium 78 in a scanning motion to generate the printed image swathby swath. Alternatively, the printhead 74 may be held in a fixedposition and the print medium 78 may be moved relative to theprinthead(s) 74. The printhead 74 can be narrower than, or as wide as,the print medium 78. In another embodiment, the printhead 74 can printto an intermediate surface, such as a rotating drum or belt (not shown)for subsequent transfer to a print medium.

With reference to FIG. 7, a flowchart S100 is depicted illustrating amethod of fabricating a lead-free piezoelectric ink-jet printhead inaccordance with an exemplary embodiment of the subject application.

The method begins with a first plating operation S102, wherein a slab ofpiezoelectric material 100 is plated on a first side with the bottomelectrode material 24. Thus, in step S102, the bottom electrode isformed. The initial thickness of the slab of piezoelectric material maybe at least about 50 μm, or at least about 100 μm.

In some embodiments, the plated piezoelectric material may be providedcommercially. In such embodiments, the method S100 may begin with stepS104, as described below.

In step S104, the plated pieces are permanently bonded to adiaphragm-plus-body assembly (the plated side towards the diaphragm)with an adhesive, or is temporarily bonded to a transfer medium, such asa carrier with double-sided tape or a carrier with adissolvable/meltable adhesive. In other embodiments, the plated materialmay be bonded to the diaphragm-plus-body assembly using other methodsknown in the art.

In step S106, the mounted pieces are thinned in a thinning operation toa thickness using at least one of a precision surface grinder, dicingsaw, a polishing wheel, or other mechanical means. In particularembodiments, the piezoelectric material 100 in a completed ink-jetprinthead may have a thickness of from about 2 μm to about 50 μm, orfrom about 4 μm to about 45 μm, or from 8 μm to about 40 μm, orpreferably from about 10 μm to about 20 μm. In an exemplary embodiment,the second thickness may be about 20 μm. In particular embodiments,where deflection of the mounted pieces are a concern, a tooled structure(patterned to fit into the body cavities) can be placed behind thediaphragm during the thinning operation to provide support.

After the piezoelectric material 100 has been plated on a first side andthinned to the desired thickness, an electrode 22 can be deposited on asecond side of the material 100 in a second plating operation S108.Thus, in this step, an electrode material layer 116 is formed. Theelectrode layer 116 may be deposited using several methods, including atleast plating, sputtering, or evaporation methods. For example, inparticular embodiments, radio frequency (RF) sputtering may be used todeposit nickel onto the second side 104 of the piezoelectric material100. It is contemplated that other methods and electrode materials maybe used.

In step S110, the piezoelectric material 100 is separated to formindividual actuators. This operation singulates each transducer,creating an individual electrically isolated element. In an exemplaryembodiment, the material 100 is diced using a dicing saw to formindividual actuators.

With reference to FIGS. 8A-8E, shown is a series of steps associatedwith producing a printhead structure with a lead-free piezoelectricmaterial according to an exemplary embodiment of this disclosure.

As shown in FIGS. 8A-8E, steps S102-S110 of method S100 are illustrated.

In FIG. 8A, a relatively thick slab of bulk piezoelectric material 100is plated on a first side 102 with a bottom electrode material 24, andforms the bottom electrode 24 of the individual actuators 26. Inparticular embodiments, the piezoelectric material 100 may have aninitial thickness 106 of from about 50 μm to about 300 μm, or from about100 μm to about 300 μm.

Next, as shown in FIG. 8B, the plated piezoelectric material 100 may bebonded to a first surface 112 of a diaphragm-plus-body assembly 30. Inparticular embodiments, the plated piezoelectric material 100 is bondedto the diaphragm 32 by bonding a first surface 110 of the bottomelectrode material 24 to the first surface 112 of the diaphragm 32. Inparticular embodiments, the plated piezoelectric material 100 may bebonded with an adhesive, or may be bonded to the diaphragm-plus-bodyassembly using other methods known in the art.

Next, as shown in FIG. 8C, the piezoelectric material 100 is thinned toa second thickness 114. The piezoelectric material 100 can be thinned toa second thickness 114 using at least one of a precision surfacegrinder, dicing saw, or other mechanical means. In particularembodiments, the second thickness 114 may be from about 2 μm to about 50μm, or from about 4 μm to about 45 μm, or from 8 μm to about 40 μm, orpreferably from about 10 μm to about 20 μm. In particular embodiments,where deflection of the mounted pieces are a concern, a tooled structure(not shown) can be placed behind the diaphragm during the thinningoperation to provide support.

Next, as shown in FIG. 8D, after the material 100 is thinned to a secondthickness 114, a top electrode material layer 116 is deposited on atleast a portion of a second side 104 (see FIG. 8A) of the material 100.In particular embodiments, the second side 104 of the piezoelectric slab100 may be plated with the top electrode material 116. In otherembodiments, the piezoelectric slab 100 may be selectively plated suchthat only a portion of the second side 104 is plated. The electrodematerial 116 may be deposited using several methods, including at leastplating, sputtering, or evaporation methods. For example, in particularembodiments, RF sputtering may be used to deposit nickel onto the secondside 104 of the piezoelectric material 100 to form the electrode layer.In particular embodiments, the top electrode layer 116 may have athickness 118 of from about 100 nm (0.1 μm) to about 1100 nm (1.1 μm).

Next, as shown in FIG. 8E, the piezoelectric material 100 is separatedinto individual actuators 26 to obtain a piezoelectric ink-jet printhead10. As previously discussed, each having a top electrode 22, a bottomelectrode 24, and a lead-free piezoelectric layer 20 disposed betweenand separating the top and bottom electrodes 22, 24. In an exemplaryembodiment, the material 100 is diced into individual actuators 26 usinga dicing saw (not shown). In some embodiments, a residual amount ofpiezoelectric material 124 may remain in the spaces (i.e. dicingstreets) 122 between each actuator 26.

With reference to FIGS. 9 and 11, additional embodiments of the methodsof making lead-free piezoelectric printheads 10 described herein aredisclosed. Like the methods described in FIG. 7, the lead-freepiezoelectric material is plated with an electrode material on one side,then attached to a substrate or device, thinned to a desired thickness,plated on a second side, and diced into individual actuators. In someembodiments, the piezoelectric material with plating on one side may beprovided commercially. In such embodiments, the first plating operationsteps described herein may be skipped. However, in the particularembodiments discussed below, piezoelectric material may be reversiblymounted onto one or more intermediate substrates, thinned while mountedon said intermediate substrates, and subsequently permanently bonded toa diaphragm of a diaphragm-plus-body assembly.

With reference to FIG. 9, a flowchart S200 is depicted illustrating amethod of fabricating a lead-free piezoelectric ink-jet printhead inaccordance with a second exemplary embodiment of the subjectapplication. In step S202, a relatively thick slab of bulk piezoelectricmaterial 100 is plated on a first side to form a first electrode layer.In particular, this piezoelectric material 100 may have an initialthickness of from about 100 μm to about 300 μm. Then, in step S204, theplated slab 100 is mounted onto an intermediate substrate, such as atransfer carrier or dicing tape.

In step S206, the piezoelectric material 100 is thinned to the desiredthickness while mounted to the intermediate substrate using at least oneof a precision surface grinder, dicing saw, or other mechanical means.In particular embodiments, the second thickness (i.e. desired thickness)may be from about 2 μm to about 50 μm, or from about 4 μm to about 45μm, or from 8 μm to about 40 μm, or preferably from about 10 μm to about20 μm.

In step S208, a second electrode material layer 116 is deposited on aleast a portion of a second side of the material 100. In furtherembodiments, the piezoelectric slab 100 may be selectively plated suchthat only a selected portion of the second side of the piezoelectricmaterial 100 is plated. The electrode material layer(s) may be depositedusing several methods, including at least plating, sputtering, orevaporation methods. For example, in particular embodiments, RFsputtering may be used to deposit nickel onto the second side of thepiezoelectric material 100 to form the electrode layer. In particularembodiments, the electrode layer may have a thickness 118 of from about100 nm (0.1 μm) to about 1100 nm (1.1 μm).

In step S210, the piezoelectric material 100 is separated intoindividual actuators 26. In particular embodiments, a dicing saw is usedto dice the material 100 into individual actuators 26.

Then, in step S210, the plated and mounted slab is reversed (i.e.flipped over) and bonded to a diaphragm of a diaphragm-plus-bodyassembly 30, thereby forming the piezoelectric printhead 10. Theintermediate substrate is then removed/unmounted from the piezoelectricprinthead 10.

Regarding FIGS. 10A-10F, one embodiment of the method shown in FIG. 9 isshown. In FIG. 10A, a piezoelectric slab material 100 with an initialthickness 106, a first surface 102, and a second surface 104, is platedon a first side 102 to form an electrode layer 116, which can have athickness 118 of from about 100 nm (0.1 μm) to about 1100 nm (1.1 μm).In FIG. 10B, the plated piezoelectric material 100 is mounted onto afirst surface 142 of an intermediate substrate 140. In particularembodiments, the intermediate substrate 140 can be, for example, atransfer carrier or dicing tape. In FIG. 10C, the piezoelectric material100 is thinned from thickness 106 to thickness 114. In FIG. 10D, thesecond surface 104 of the piezoelectric material 100 is plated with anelectrode material to form a second electrode layer 24 with a top (orouter) surface 110. In FIG. 10E, a dicing operation is performed inwhich individual actuators 26 are isolated. Specifically, the dicingoperation forms dicing streets 122 between individual actuators 26, andeach actuator 26 may include a piezoelectric material layer 20 that isplated on one side with a top electrode 22 and plated on the another (oropposite) side with a bottom electrode 24. In other words, the topelectrode 22 is adjacent to the piezoelectric material on one side, andthe bottom electrode 24 is adjacent to the piezoelectric material onanother side. Finally, in FIG. 10F, a bonding operation is performedwherein individual actuators 26 are bonded to a diaphragm 32 of adiaphragm-plus-body assembly 30, and the intermediate substrate 140 isremoved/unmounted from the actuators 26, thereby forming a piezoelectricink-jet printhead 10.

Similarly, with reference to FIG. 11, a flowchart S300 is depictedillustrating a method of fabricating a lead-free piezoelectric ink-jetprinthead in accordance with a third exemplary embodiment of the subjectapplication.

In step S302, a first surface of the slab of piezoelectric bulk materialis plated to form a first electrode layer. In particular embodiments,the piezoelectric material 100 may have an initial thickness of fromabout 100 μm to about 300 μm.

In step S304, the plated material 100 is mounted onto a firstintermediate substrate. In particular embodiments, the firstintermediate substrate may be a thinning medium. In some embodiments,the thinning medium may be a wafer.

In step S306, the piezoelectric material 100 is thinned to a desiredthickness using at least one of a precision surface grinder, dicing saw,or other mechanical means. In particular embodiments, the thinnedpiezoelectric material 100 may have a desired (or second) thickness offrom about 2 μm to about 50 μm, or from about 4 μm to about 45 μm, orfrom 8 μm to about 40 μm, or preferably from about 10 μm to about 20 μm.

In step S308, another electrode material layer is deposited on at leasta portion of a second side of the piezoelectric material 100. Inparticular embodiments, the second side of the piezoelectric slab 100may be plated with the electrode material. In further embodiments, thepiezoelectric slab 100 may be selectively plated such that only some ofthe second side is plated. The electrode material layer may be depositedusing several methods, including at least plating, sputtering, orevaporation methods. For example, in particular embodiments, RFsputtering may be used to deposit nickel onto the second side of thepiezoelectric material 100 to form the electrode layer. In particularembodiments, the electrode layers may have a thickness of from about 100nm (0.1 μm) to about 1100 nm (1.1 μm).

In step S310, the plated and thinned piezoelectric material 100 is thenmounted to a second intermediate substrate. In particular embodiments,the second intermediate substrate may be a transfer carrier or dicingtape.

In step S312, the plated and thinned piezoelectric material 100 isunmounted from the first intermediate substrate (i.e. thinning medium).

Then, in step S314, the plated material 100 can be diced into individualactuators 26. In particular embodiments, a dicing saw is used to isolatethe individual actuators.

Then, in step S316, the plated piezoelectric material 100 is flipped andbonded to a diaphragm of a diaphragm-plus-body assembly, and theactuators 26 are removed/unmounted from the second intermediatesubstrate, thereby forming the piezoelectric ink-jet printhead 10. Inparticular embodiments, when the actuators 26 are bonded to thediaphragm, there are no intermediate layers between the piezoelectricmaterial 100 and the diaphragm except for the electrode layer (i.e. thebottom electrode layer).

Regarding FIGS. 12A-12H, one embodiment of the method illustrated inFIG. 11 is shown. In FIG. 12A, a piezoelectric slab material 100 with aninitial thickness 106, a first surface 102, and a second surface 104, isplated on a first side (i.e. the first surface 102) to form an electrodelayer 24 having a thickness 108. In FIG. 12B, the plated piezoelectricmaterial 100 is mounted onto a surface 152 of a first intermediatesubstrate 150. In some embodiments, when the plated piezoelectricmaterial 100 is mounted onto the first intermediate substrate 150,surface 152 of the intermediate substrate is adjacent or contacting asurface 110 of the electrode layer 24. In particular embodiments, thefirst intermediate substrate 150 can be a thinning medium, for example,a wafer or a glass block. In FIG. 12C, the piezoelectric material 100 isthinned from thickness 106 to thickness 114. In FIG. 12D the surface 104(i.e. the surface opposing surface 102 that was previously plated withelectrode layer 24) of the piezoelectric material 100 is plated with anelectrode material to form an electrode layer 116 having a surface 120and a thickness 118. In FIG. 12E, the plated piezoelectric material 100is mounted onto a second intermediate substrate 140 such that surface120 of electrode layer 116 is adjacent and contacting surface 142 of thesecond substrate 140. In particular embodiments, the second intermediatesubstrate can be, for example, a transfer carrier or dicing tape. InFIG. 12F, the plated piezoelectric material 100 is unmounted from thefirst intermediate substrate 150. In FIG. 12G, the piezoelectricmaterial 100, and electrode layers 116, 24 are diced to form individualactuators 26. As discussed above, this dicing operation forms dicingstreets 122 between individual actuators 26. Finally, in FIG. 12H, themounted actuators 26 are flipped, bonded to a diaphragm 32 of adiaphragm-plus-body assembly 30, and removed/unmounted from the secondintermediate substrate 140, thereby forming the piezoelectric ink-jetprinthead 10.

Some portions of the detailed description herein are presented in termsof algorithms and symbolic representations of operations on data bitsperformed by conventional computer components, including a centralprocessing unit (CPU), memory storage devices for the CPU, and connecteddisplay devices. These algorithmic descriptions and representations arethe means used by those skilled in the data processing arts to mosteffectively convey the substance of their work to others skilled in theart. An algorithm is generally perceived as a self-consistent sequenceof steps leading to a desired result. The steps are those requiringphysical manipulations of physical quantities. Usually, though notnecessarily, these quantities take the form of electrical or magneticsignals capable of being stored, transferred, combined, compared, andotherwise manipulated. It has proven convenient at times, principallyfor reasons of common usage, to refer to these signals as bits, values,elements, symbols, characters, terms, numbers, or the like.

It should be understood, however, that all of these and similar termsare to be associated with the appropriate physical quantities and aremerely convenient labels applied to these quantities. Unlessspecifically stated otherwise, as apparent from the discussion herein,it is appreciated that throughout the description, discussions utilizingterms such as “processing” or “computing” or “calculating” or“determining” or “displaying” or the like, refer to the action andprocesses of a computer system, or similar electronic computing device,that manipulates and transforms data represented as physical(electronic) quantities within the computer system's registers andmemories into other data similarly represented as physical quantitieswithin the computer system memories or registers or other suchinformation storage, transmission or display devices.

The exemplary embodiment also relates to an apparatus for performing theoperations discussed herein. This apparatus may be specially constructedfor the required purposes, or it may comprise a general-purpose computerselectively activated or reconfigured by a computer program stored inthe computer. Such a computer program may be stored in a computerreadable storage medium, such as, but is not limited to, any type ofdisk including floppy disks, optical disks, CD-ROMs, andmagnetic-optical disks, read-only memories (ROMs), random accessmemories (RAMs), EPROMs, EEPROMs, magnetic or optical cards, or any typeof media suitable for storing electronic instructions, and each coupledto a computer system bus.

The algorithms and displays presented herein are not inherently relatedto any particular computer or other apparatus. Various general-purposesystems may be used with programs in accordance with the teachingsherein, or it may prove convenient to construct more specializedapparatus to perform the methods described herein. The structure for avariety of these systems is apparent from the description above. Inaddition, the exemplary embodiment is not described with reference toany particular programming language. It will be appreciated that avariety of programming languages may be used to implement the teachingsof the exemplary embodiment as described herein.

A machine-readable medium includes any mechanism for storing ortransmitting information in a form readable by a machine (e.g., acomputer). For instance, a machine-readable medium includes read onlymemory (“ROM”); random access memory (“RAM”); magnetic disk storagemedia; optical storage media; flash memory devices; and electrical,optical, acoustical or other form of propagated signals (e.g., carrierwaves, infrared signals, digital signals, etc.), just to mention a fewexamples.

The methods illustrated throughout the specification, may be implementedin a computer program product that may be executed on a computer. Thecomputer program product may comprise a non-transitory computer-readablerecording medium on which a control program is recorded, such as a disk,hard drive, or the like. Common forms of non-transitorycomputer-readable media include, for example, floppy disks, flexibledisks, hard disks, magnetic tape, or any other magnetic storage medium,CD-ROM, DVD, or any other optical medium, a RAM, a PROM, an EPROM, aFLASH-EPROM, or other memory chip or cartridge, or any other tangiblemedium from which a computer can read and use.

Alternatively, the method may be implemented in transitory media, suchas a transmittable carrier wave in which the control program is embodiedas a data signal using transmission media, such as acoustic or lightwaves, such as those generated during radio wave and infrared datacommunications, and the like.

It will be appreciated that variants of the above-disclosed and otherfeatures and functions, or alternatives thereof, may be combined intomany other different systems or applications. Various presentlyunforeseen or unanticipated alternatives, modifications, variations orimprovements therein may be subsequently made by those skilled in theart which are also intended to be encompassed by the following claims.

What is claimed is:
 1. A method of making a piezoelectric ink-jetprinthead comprising a lead-free piezoelectric material, the methodcomprising: bonding the piezoelectric material to a diaphragm-plus-bodyassembly, wherein the piezoelectric material is plated with a firstelectrode material on a first side; thinning the piezoelectric materialto a first thickness; plating the piezoelectric material on a secondside with a second electrode material; and dicing the piezoelectricmaterial into individual actuators; wherein the lead-free piezoelectricmaterial comprises bismuth sodium potassium titanate (BNKT) and at leastone of bismuth magnesium titanate (BMT) and niobium potassium sodium(KNN).
 2. The method of claim 1, wherein the method further comprisesplating the piezoelectric material on a first side prior to bonding thepiezoelectric material to the diaphragm-plus-body assembly.
 3. Themethod of claim 1, wherein the first thickness of the piezoelectricmaterial is from about 50 μm to about 300 μm.
 4. The method of claim 1,wherein the second thickness of the piezoelectric material is from about2 μm to about 50 μm.
 5. A method of making a piezoelectric ink-jetprinthead comprising a lead-free piezoelectric material, the methodcomprising: mounting the piezoelectric material onto a firstintermediate substrate, wherein the piezoelectric material is plated ona first side with a first electrode material; thinning the piezoelectricmaterial to a first thickness; plating the piezoelectric material on asecond side with a second electrode material; dicing the platedpiezoelectric material into individual actuators; and bonding the dicedpiezoelectric actuators to a diaphragm; wherein the piezoelectricmaterial comprises bismuth sodium potassium titanate (BNKT) and at leastone of bismuth magnesium titanate (BMT) and niobium potassium sodium(KNN).
 6. The method of claim 5, wherein the method further comprisesplating a first side of the piezoelectric material with a firstelectrode material prior to mounting the piezoelectric material onto afirst intermediate substrate.
 7. The method of claim 5, wherein themethod further comprises: mounting the plated piezoelectric materialonto a second intermediate substrate after plating the piezoelectricmaterial on a second side with a second electrode material; andunmounting the plated piezoelectric material from the first intermediatesubstrate.